1. Field of the Invention
The present invention relates to a magnetic disk recording and/or reproducing apparatus. In particular, it relates to an apparatus utilized with a magnetic disk media on which preformatted signals such as a servo signal for positioning a head and an address signal are previously formed by uneven surfaces.
2. Background of the Invention
Recently, research and development have been performed on a hard disk drive with a magnetic disk which was manufactured by providing uneven surfaces on its substrate and by then coating a magnetic layer thereon. A servo signal for positioning a head on a magnetic disk has been proposed, as shown in FIG. 7A and FIG. 7B. FIG. 7A shows a plan view of an entire disk and FIG. 7B shows an enlarged plan view of an important portion of the disk. As shown in these drawings, there is a Data area (D) in tracks extending along a peripheral direction of a disk 10 and a Servo area or segment (S) along a radial direction of the disk 10 in which servo patterns are formed by uneven surfaces such as pits and lands in an optical disk.
When this disk starts rotating, a slider floats on the disk. Because of the uneven portions repeatedly formed around a track, the floating height of the slider may be varied as the disk rotates. A spacing may also vary between a magnetic head mounted on the slider and a magnetic layer of the disk. It causes a variation of a reproducing voltage. In the worst case, the slider would touch with the disk and generate the risk of crushing the head.
To avoid this variation of floating height, a method has been proposed for filling the hollowed portions of the pattern with resin so as to make them flat. However, it is very difficult to obtain a precise flatness by this method. In other words, when providing a polish to expose the magnetic layer after filling the uneven portions with resin, it is difficult to make them flat. This may be caused by the difference of hardness between the magnetic layer and the resin as a filling material, which may result in delicate uneven portions. In practice, a floating height of up to approximately 0.1 .mu.m is utilized. But, it is desired to realize the floating height of around 0.05 .mu.m to achieve a higher recording density. However, the above method for filling and flattening may not be suitable to obtain a surface which is flat enough for maintaining the floating height at a constant level.